SiC (silicon carbide) shows a lower electrical insulation and a smaller energy loss at the time of electrification as compared to silicon and thus has a smaller calorific value as well as higher heat resistance. Therefore, as compared to silicon power semiconductors, SiC power semiconductors are capable of handling a larger electric power, so that SiC power semiconductors are being actively studied as next-generation power semiconductors that would replace silicon power semiconductors that are widely used at present. The heat-resistance limit temperature of silicon power semiconductor devices is about 150° C.; however, in SiC power semiconductor devices, the use thereof at a temperature of 240 to 300° C. is being investigated so as to handle a larger electric power, and heat resistance of higher than 240° C. is demanded also for the members of SiC power semiconductor devices.
Conventionally, as a molding resin of a semiconductor obtained by molding a resin, an epoxy resin is mainly used. In general, the physical properties of a resin, such as viscoelasticity and thermal expansion coefficient, largely changes across its Tg (glass transition temperature); therefore, it is required that the Tg of a molding resin be higher than the service temperature of the semiconductor. However, since the Tg of conventional epoxy resins is about 200° C. or lower, there are problems of material softening, crack generation and the like under such a service environment where the temperature exceeds 240° C. (see, for example, Patent Documents 1 and 2). In addition, since epoxy resins having a Tg of 240° C. or higher have high pre-curing melting points, their curing temperatures are also high and curing requires a long time, so that there are problems that other members are adversely affected and the productivity is reduced (see, for example, Patent Document 3). Furthermore, although the use of resins other than epoxy resins, such as polyimide, has also been studied (see, for example, Patent Document 4), such resins are not satisfactory in terms of required performance.
Meanwhile, curable compositions containing a vinylbenzyl ether compound of a polyvalent phenol compound are also known (see, for example, Patent Documents 5 to 7); however, all of these curable compositions have a Tg of lower than 240° C. and are thus not satisfactory as molding resins of SiC powder semiconductors.